GM Hy-wire

A vehicle that teeters high above customer demandwithout a net.

March 2003 By FRANK MARKUS

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We've driven the car of the future. It doesn't fly, it doesn't drive itself, and it looks like a car instead of some outrageous GM Motorama dream machine such as the winged, finned, turbine-powered Firebirds of yore. This one is serious, in keeping with the serious cash GM is investing ("hundreds of millions," they say) in a program that has generated 30-plus patents to date. The Hy-wire, which was shown at the Paris auto show last fall, is the running proof-of-concept incarnation of the AUTOnomy concept from the 2002 Detroit show and as such offers a view of the future through three portals.

First, there's the idea of the high-value, long-lasting, fully integrated "skateboard" running chassis, to which a wide range of bodies could be docked. Next, there's the drive-by-wire control system. And finally, there's the hydrogen fuel-cell powertrain. These concepts will likely arrive one at a time on different vehicles, but the crystal-ball folks at GM have integrated them here.

The skateboard concept promises a low, Corvettelike center of gravity for improved handling and unlimited packaging flexibility in the bodywork. Concentrating the high-investment mechanicals into a chassis with a 20-year life span permits the body to become a high-profit fashion item in which the form is constrained by far fewer functional boundaries. Drive-by-wire permits the driver to sit on the right or left, control feel can be tailored to the driver's tastes or mood, and it's an enabler for technologies such as automated highways. And the hydrogen-powered fuel cell, which emits only water, promises to distance the automobile from the environmental debate and partly insulate the auto industry from unpredictable fluctuations in the oil industry (most hydrogen is produced from domestic natural gas). That's a lot of hope packed into one 4200-pound concept car.

The Hy-wire's snap-on body offers an airy, luxurious environment for five with open areas from the seats forward to the nose and rearward to the tail. It attaches via 10 mounting points (plus one electrical connector) to an all-aluminum, control-arm-suspended rolling chassis that is 11 inches thick. It packages a 94-kW fuel cell, which draws hydrogen from three 5000-psi compressed-hydrogen tanks to power an 80-hp electric motor driving the front wheels. The tanks hold 4.4 pounds of hydrogen (containing the energy equivalent of two gallons of gas) good for an 80-mile range. Motors in each wheel and 10,000-psi tanks are but a few of the improvements expected to lead to a six-inch-thick skateboard chassis with a 170-mile range.

Hydrogen Today

Fuel cells return nearly twice the efficiency of the best diesels from the energy in the fuel, but factor in total energy input upstream of the tank, and hydrogen's advantage falls to as low as 10 percent.

The current level of hydrogen production could power 15 percent of the transportation segment.

There are no booster batteries onboard, so there is no regenerative braking. This was done partly to conserve weight and package space and also to illustrate that the fuel cell can produce sufficient electricity on demand. We're not entirely convinced of this argument. Step-off is lively, as in any electric car (peak torque is at 0 rpm), but the Hy-wire seemed to experience some lag, especially when accelerating as if to pass. Order up acceleration, and one can hear the air compressor and the various hydrogen control valves clicking over the whir of the drive motor. Acceleration is a leisurely 10 seconds to 40 mph.

The Swedish firm SKF engineered the Hy-wire's drive-by-wire system using much of the same hardware found in the Bertone Filo concept (Upfront, November 2001) but with greatly improved software. Two twist grips arranged like an airplane's control yoke manage the steering, the braking, and the acceleration. To accelerate, twist the grips, knuckles back as on a motorcycle; squeeze the grips for braking; and steer them through just 20 degrees to hang a U-ey.

Although the Hy-wire's steering suffered less of the drunken-sailor constant overcorrection problem we reported in the Filo, this concept still needs a lot of work. Our wrists were only comfortable at the equivalent of half-throttle. Also, very little brake feel is synthesized through the grips, and 20 degrees just aren't enough to allow for precise placement of the car in tight quarters or on a driving line (human wrists couldn't work the accelerator and brake under any more steering lock). We also had to consciously remember to back off the gas when hitting the brakes. It begs the question: Why should a driver's feet be excused from all duty? But here's the nail in this system's coffin: It's impossible to drive with one's knees while multitasking.

So what does the future as depicted by the Hy-wire bode for the enthusiast? A hunkered-down chassis with four individual wheel motors capable of all-wheel drive, braking, and yaw control sounds like good news on the dynamic front, presuming good by-wire control feel can be synthesized. Power upgrades will take the form of new software or the addition of fuel cells to the stack, and the whole system promises to be more upgradable, like a modern computer.

And how far off is this bold future? GM hopes that between 2010 and 2020 it will become the first company to sell one million fuel-cell vehicles. The cost of fuel cells has plummeted in the past few months but is still up by a factor of 10 over the cost of a conventional drivetrain. Technology is marching forward (see sidebar) to further reduce cost, increase range, and lower the minimal operating temperature (it's down to minus four degrees Fahrenheit, but 40 below is the target for North American vehicles). The big unknown is the refueling infrastructure. Hydrogen production is increasing about eight percent yearly, and a network of refueling stations in cities is foreseeable within 20 years.

You know what they say: Where there's a will, there's a way—and the planet's largest automaker is investing an awful lot of will these days.

While GM's glitzy Hy-wire show car is off grabbing headlines, the HydroGen series of workaday Opel Zafira mini-minivans has been slogging through the development process of making a hydrogen fuel cell marketable and manufacturable. At this third stage of the game, all the hardware fits completely out of sight. The fuel cell, the traction motor, the compressors, and most of the plumbing (along with a working air conditioner!) have been integrated into a module that mounts into the stock bodywork using the same tooling that installs the internal-combustion drivetrain. The hydrogen storage tanks require a bump in the flat floor beneath the second-row seats, but the rest of the cargo area is clear.

Liquid and compressed-gas storage systems are both being developed. The package envelope can accommodate a double-walled, vacuum-insulated steel tank containing 10 pounds of liquid hydrogen at minus 453 degrees Fahrenheit, good for a 250-mile range, or two carbon-fiber-reinforced, 10,000-psi tanks that hold 6.8 pounds for 170 miles. The trouble with liquid is that unless the car is driven at least 15 miles a day, some hydrogen boils and is burned off through a catalyst. A tank full of sodium-and-aluminum powder that binds with hydrogen to form alanate is under development. Its benefit is that it releases hydrogen at roughly the fuel-cell stack's operating temperature (120 to 190 degrees), but it releases the hydrogen too slowly, it expands by 30 percent in the process, and it's slow to refuel. GM is not actively pursuing the sodium borohydride (soapy water) hydrogen storage method, because the overall energy density of the system, including catalysts, heat exchangers, and spent borax storage, is believed to be noncompetitive.

Developments inside the fuel cell are focusing on refining the pattern of channels etched on the anode and cathode plates to optimize air and hydrogen flow over the catalytic proton-exchange membrane (PEM) where the electricity is generated, and on improving the material used in that membrane. The current Teflonlike material (known as PTFE) is fragile and requires precise control of temperature, pressure, and humidity. Improved robustness would reduce the need for these control systems, thereby also reducing cost and improving efficiency and cold-weather performance. Right now, the individual cells produce about one horsepower per square foot of PEM, and the system needs 30 seconds from "key on" to "drive away" at four degrees below zero.

HydroGen3 uses no booster battery, so it can't recapture braking energy. (Using this energy to regenerate hydrogen is tricky, as the pressure and voltage required to divorce those happy H2O molecules in the fuel cell are much higher than what's needed for the marriage—kind of like life.) Adding a battery and regenerative braking would boost efficiency on the federal city-driving loop (FTP 75) by 1.6 percent. Shutting the fuel cell off at idle could save another 2.8 percent.

As it is, the HydroGen3 weighs about 400 pounds more than the Zafira it's based on, but it zips around town with acceptable acceleration, and it'll do 99 mph. It has even passed computer crash-test simulations. Based on our brief drive around Monaco, we're cautiously optimistic that a fuel-cell future might be a tolerable world for car folks.